1. Field of the Invention
The present invention relates to a zoom lens, and particularly to a zoom lens for projection applicable to a projection-type display apparatus.
Further, the present invention relates to a projection-type display apparatus including such a zoom lens for projection.
2. Description of the Related Art
Recently, projection-type display apparatuses, such as a transmission-type or reflection-type liquid crystal display apparatus and a DMD display apparatus, using light valves became widely used. Projection lenses used in such kinds of projection-type display apparatuses generally need to have long back focus. Further, an entrance pupil of such a projection lens viewed from a reduction side (light valve side) needs to be located sufficiently far. In other words, the projection lens needs to have telecentricity on the reduction side. Further, the projection lens needs to have a variable magnification function (zoom function), considering the portability of the apparatus and the adaptability of the apparatus to setting conditions. Further, the projection lens needs to have a wide angle of view to satisfy a requirement of projection onto a large screen from a short distance.
Conventionally, for example, the following Japanese Unexamined Patent Publication No. 2007-248840 (Patent Document 1), Japanese Unexamined Patent Publication No. 2007-328163 (Patent Document 2), and Japanese Unexamined Patent Publication NO. 2010-282147 (Patent Document 3) and the like proposed five-group zoom lenses, in which three lens groups are moved during magnification change. Further, the zoom lenses are configured to be telecentric on a short conjugate length side, in other words, a reduction side.
In the zoom lenses disclosed in Patent Documents 1 through 3, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having positive refractive power are arranged in this order from a magnification side. The zoom lenses are configured in such a manner that the first lens group and the fifth lens group are fixed while the second lens group through the fourth lens group move during magnification change. The zoom lenses are configured so as to suppress a fluctuation of various aberrations caused by magnification change to a relatively low level.